If you're using DJI Assistant 2 then the program downloads them, it should show you a list of the firmware versions available.
If DJI Assistant 2 doesn't show you previous firmware versions available then you could try using the free dronehacks...
I don’t know about the plus batteries, but I’d be wondering what is going on if it were the standard batteries.
Are you sure the power supply you are using is powerful enough? Can the USB cable carry that power? I ended up with a 100w from Anker...
Your guess as to what happened doesn't make sense.
A motor froze ??
Have you ever felt how hot your motors run ?
They are the last part of a drone that will freeze.
A motor "failed" ?
How do you know this?
What did you experience that led to...
And the CAA might just have made this whole discussion meaningless, (at least in the UK). There is a report on Geeksvana that the CAA have had a policy review and concluded that while green flashing lights are meant to help people on the ground...